Tensile and Dynamic Toughness of Kenaf Fiber-Reinforced Epoxy Composites

The environmental impact of petroleum-based materials in driving climate change has stimulated growing interest in natural lignocellulosic fibers (NLFs) as reinforcements for polymeric matrices. NLFs exhibit specific mechanical properties that, in some cases, rival those of synthetic fibers such as aramid, carbon, and glass. Among the wide variety of NLFs, kenaf has been extensively investigated in applications including textiles, construction, and furniture, owing to its long-established global cultivation. Previous studies have also demonstrated its potential as a reinforcement in polymeric matrices for engineering applications, including ballistic protection. In this context, the present work reports, for the first time, on the tensile and dynamic impact toughness of epoxy matrix composites reinforced with 10, 20, and 30 vol% kenaf fibers. The tensile toughness, defined as the area under the stress–strain curve up to fracture, ranged from 9.36 kJ/m2 at 10 vol% to 52.30 kJ/m2 at 30 vol% fiber content—representing a three- to tenfold increase compared to the neat epoxy matrix. In Izod impact tests, the composites containing 30 vol% kenaf fibers absorbed 22 times more energy than the neat epoxy, rising from 1.8 to 38.8 kJ/m2. On average, the tensile toughness values exceeded those of the corresponding dynamic impact toughness. Scanning electron microscopy revealed the fracture morphology and highlighted the influence of the fibers under both toughness conditions.